The present invention relates to arbor-mounted hole saws, and more particularly to a quick-release arbor for receiving multiple sized pilot drill bits press fit into pilot shafts.
A hole saw is a saw blade of annular shape, whose annular kerf creates a hole in the workpiece without having to cut up the core material. It is used in a drill. Hole saws typically have a pilot drill bit at their center to keep the saw teeth from walking. The fact that a hole saw creates the hole without needing to cut up the core often makes it preferable to twist drills or spade drills for relatively large holes (especially those larger than 25 millimeters (1.0 inch)). The same hole can be made faster and uses less power.
The depth to which a hole saw can cut is limited by the depth of its cup-like shape. Most hole saws have a fairly short aspect ratio of diameter to depth, and they are used to cut through relatively thin workpieces. However, longer aspect ratios are available for applications that warrant them.
The hole saw consists of a metal cylinder, usually steel, mounted on an arbor. The cutting edge either has saw teeth formed in it or industrial diamonds embedded in it. The arbor can carry a drill bit to bore a centering hole. After the first few millimeters of cut, the centering mechanism may no longer be needed, although it will help the bit to bore without wandering in a deep hole. The sloping slots in the cylinder wall help carry the dust out. The kerf of the cut is designed to be slightly larger than the diameter of the rest of the hole saw so that it does not get jammed in the hole.
Holes saws for use with portable drills are commonly available in diameters from 6 to 130 mm (0.24 to 5.12 in). The only limit on the length of the cylinder, and thus depth of the hole, is the need to remove the bit from the hole to clear dust. A 300 millimeters (12 in) cylinder length is not uncommon, although shorter bits are usual. By breaking the core off from time to time and using a shank extension, a diamond core drill can drill to depths many times its length.
Saw teeth are used for most materials, such as wood, plastic, soft plaster, and metal. Diamond hole saws are used to bore holes in brick, concrete, glass, tile, porcelain tiles, granite, marble, or any lapidary material and stone. Not all materials to be drilled are suitable for dry drilling. Very hard materials like reinforced concrete normally should be drilled with water, otherwise the excessive heat generated during the drilling process may cause the diamonds on the core bit to become blunt, and then lead to poor drilling performance.
The main advantage over conventional drill bits is the hole saw's efficiency, because very little of the total material being removed is actually cut, which ultimately reduces the overall power requirement. Another advantage over drill bits is the wider size capability. For example, a 100 millimeters (3.9 inches) hole would require a huge twist drill or spade drill, unable to be properly driven by a pistol-grip drill or benchtop drill press; but it can be cut with a hole saw with relative ease.
Referring to prior art FIGS. 1 through 3, the parts and operation of a traditional hole saw 26 maybe understood. A hexagonal pilot shaft 10 fits into a drill or drill press (not shown) and the pilot shaft supports a pilot drill bit 12 which is typically press fit into the other end of the pilot shaft 10. The pilot shaft 10 is then passed through a hexagonal central passage and securely mounted within the arbor 14 by a threaded key hole and set screw 16 bearing down upon the pilot shaft 10. Biased axially moveable (along arrows A) collar 18 has depending hole saw index pins 20. Below the pins 20 is threaded hole saw male fitting 22. The hole saw 26 is cylindrical with teeth 28 and a bottom wall 30. In bottom wall 30 is threaded central aperture or hole 32. Indexing locking holes 34 mate with arbor index pins 20. Sloping dust out slots 36 are provided to minimize clogging of the hole saw 26 in the work piece.
Once the pilot shaft 10 is secure in arbor 14, collar 18 is moved away from threaded fitting 22 moving index pins 20 out of the way for the threaded fitting to be threaded into hole saw 26 threaded central aperture 32. Thereafter, the collar is rotatably adjusted and released to secure pins 20 into locking holes 34. The arbor 14 and hole saw 26 are secured together for operation. This process can be time consuming. By this arrangement, the arbor 14 and hole saw 26 are not overtightened by operation of the tool.
Referring to FIGS. 4 and 5, one structure for a quick-change arbor 40 for a hole saw 38 maybe seen and is further disclosed in U.S. Pat. No. 7,934,893 and incorporated here by reference. Arbor 40 has a hexagonal central aperture 42 for a pilot shaft 44 with a pilot drill bit 46. The shaft 44 has an annular channel or notch 48. The arbor has a biased latch 50 mounted in the arbor 40 and pivotal on pin 52. Latch 50 is depressed as to align with annual channel 48 to be secured therein or to be released therefrom.
This style of hole saw 38 does not use indexing pins 20 and locking holes 34 to secure the hole saw 38 and arbor together 40. By this arrangement, the hole saw 38 and arbor 40 may be overtightened and difficult to separation when not in use. Also, the drill press or manual pressure that is exerted to advance the hole saw has a tendency to wear on the biased latch which can lead to failure.
There is a need for a quick-release arbor for a hole saw that secures, but does not allow overtightening, of the arbor to the hole saw with a finger grip on the axially movable collar for easy threading of the arbor into the hole saw.